Short wave transmission



Dec. 12, 1933. 1.. E. HUNT SHORT WAVE TRANSMISSION Filed July 21, 1932 FIG.

FIG. 2

INVENTOR L. E. HUNT BY ATTORNEY "80 in connection open at one ends-and eaming and 1C rare the and-the Patented Dec. 12,1933

' snow WAVE TRANSMISSION Loyd E. Hunt; Eatonto'wn, N. J., alssignor to Bell Telephone Laboratories, Incorporated, New;

corporation of New York Application ti 21. 1932. seem rte nasal B (Cl. 17844) 5 This meanest relates to short wave transmission wave length from or one twelfth or the length or me.

The invention will be more readily understood by reference to the tollowingdetafled description with the accompanying drawing ,I- .1 I Lisa. cfiiu'ammatic circuitto which re:-

crence-is made in explaining. the invention, and a Fig; 2. shows an applicati' or-wthe invention meann ss V n I acben'stic v cez havinginegligible resistance and:

, formed o1'.--twopara11elwires,

cuited end is given by the equation 7 V ;-:Z =iZotank0- (1r andthe pedancezs bokingtcwardtheopm sc 1 H l="-J' T where "o=a g1 r 1.

frequency, say In, that is, if [is 2, then equation respectively, per unit length =2w times the frequency.

- The impedance Z of the two portions of the section in paralleL'as seen from P of the line, and

n will be noted that a at some (3) becoxnes Or, substituting cot lag for tan (1-k)g in the denominator, Equation (4) becomes 'z nmkg z=- (5) 1 -tan k cot k E as k is not equal to zero.

On the other hand,"Z is equal to zero if tan (1-I c)0 that is, if

is any odd integer. Taking the condiwhere n tion where 'n is unity andjinserting for 0 its value 1 where x" is the wave Iength'of the wave "td be v suppressed it appears that V V. A!

It rene s then that u the section ot'line flsed as a suppressor is connected to the transmission i107 istance from the open end of the secequal to then an effective short circuit is provided for the Since the suppressor S offers a high impedance to this frequency will 6 V V will be suppressed and prevented from reaching transmission line TL to the wave which has a length equal to A. Thus, if it is desiredto suppress the third harmonic, then In =a. )tandtl k)l 12 The suppressor section equal to 4 i and the point P at which connection the transmission line is made will be adistance i from theopen end of the section ofline.

Fig. 2 shows anembodiment of the invention in a transmission line TL which leads from a generator E to'an antenna A. The line is coupled to the antenna. through transformer T, The antenna is connected to one terminal of a winding of the transformer and the other terminal of this winding is grounded at G. Generator Eris a single' frequency source of alternating yoltage of fundamental frequency In, but there are also present frequencies which are harmonics of the fundai mental, as'for example, the third harmonic, which has a frequency of 3 in. The section of line S which; serves as the suppressor is bridged across the transmission line at a point P preferably near the generator. The suppressor S is a uniform section of transmission line comprising two parallel wires, short-circuited at the end B and open at the end C. The length of the suppressor section isequalto v 3 v r 4" where x is the wave length correspondingr to the fundamental frequency In of the generator, which is to, be conducted along the antenna A. Assuming that it is desiredto suppress the third harmonic then the distance (l -k)l from the open end C of S, to the point of connection Bis made equalito H I v The distance "from? tostheshort-circuite d end B will, of course, be equal to q x the fundamental frequency is, be freely transmitted along the line TL to the antenna, but asS is effectively ashort circuitacross the line for the third harmonic 3 fa, this frequency the antenna.

The suppressor may, of course, be designed to ,suppress any other harmonic by making the length (1-k)l equal to. p u a ,where h is :the order of the harmonic con'- line, the length w to one-quarter of the length of will then have a length l I short-circuited at one end and open s'aidfirst-menti'cined transmission ftance from the open end of said section of line equal to one-quarter of sponding to a=frequency which is a harmonic of the frequency generated by said wave I 6: In a wave tr The supressor section S may be either an open wire transmission line or a concentric conductor line, since the principles here presented apply equally will to either form.

What is claimed is:

1. In a wave transmission system, a wave source, a transmissionline connected thereto and a uniform section of transmission line bridged across said first-mentioned transmission of said section of line being equal the wave generatsource, said section of line being at the other bridged across line at a dised by said wave end and said section of line being the wave length corresource.

'2. In combination, a single frequency wave sourcein which'harmonics are present,.a transmission'line connected thereto and auniform section of transmission line bridged across said firstmentioned transmission line, the length of said section of ,line, being equal to one-quarter of the I length ofythe fundamental wave of said wave source, said section of line being short-circuited at one end and open at the otherand bridged across said first-mentioned transmission line at a-distance fromthe open end of said section of ,linerequal to one-quarter. of the wave length of the third harmonic of .the fundamental frequency 1 of saidwave'source, '4 Y a 3.'In1 a wave, transmission system, at-wave source,a transmission'line leading'therefrom and a harmonic suppressonsaid harmonic-suppressor comprising two sections of uniform transmission line connected in parallel and bridged'across said first-mentioned transmission line, one ofsaid sections beingeopen-circuited-at the far endland 116 the other of saidsectionsb'eing short-circuited at: the; far end and. of. twice, the length of: said one section,and the sum of the lengths of said two; sectionsv being equal to one-fourth of the length .of the fundamental wave of said wave 120 source. w a 1 4. In a wave transmission system a wave 'source,' ,a transmission line leading therefrom, and-a thirdharmonic suppressor, said suppressor comprising t, osections of. transmission line connected in parallel and bridged across said firstmentioned transmission line, one of said sections being short-circuited at the far end and the other of said sections beingLopen-circuited at' the far end and of a length equal .to one-twelfth ofthe length-of thej'wave corresponding to vthe fundamentalfrequency of; said wave source, and the sum of the lengths" of said two sections of line being equal to one fourth of the length of-the-fundamental-ware of said wave source. 1

uniform section of transmission line bridged across said first-mentioned transmission line, the

length of said section of'line being equal to onequarter of the length of the fundamental wave of said wave. source, said section of line being short-circuited at one end and open at the other and the bridging point being at'a distance from the open end of said section equal to one-third of the length of said section of nae;

nnssion system,

a si'ngle irequency wave source in which harmonic frequencies are present, a transmission line connected V thereto and a section of concentric conductor transmission line bridged across'said first-mentioned transmission line, the length of said sec tion 01 line being equal to one-quarter of the length or the fundamental wave of said wave source, said section or line being short-circuited LOYD E. HUNT. 

